XX INTRODUCTION 



a strap, from which it sends out tubular cells that might 

 be called clamp cells. So strongly do they penetrate that 

 when one pulls the outer flakes of bark will come ofF, but 

 the cells will not loose their hold. A few such roots, how- 

 ever, serve to hold the orchid in place, while the rest, growing 

 out without touching anything, hang down from the tree 

 like long threads, or grow freely in the air in tortuous shapes 

 like ropes. In some orchids regular tassels of such roots 

 hang down. 



Simple as the aerial roots seem, they are more complex 

 than the roots that plunge in the earth to pursue their food 

 around stones and through crevices. They are covered by 

 a white membrane composed of perforated cells that absorb 

 water like a sponge. As soon as the air becomes moist, 

 whether from falling rain or humidity, they immediately 

 imbibe its water, and pass it on to chlorophyl cells that 

 are imbedded in the centre, and these in turn with the help 

 of the leaves begin the slow mysterious process of accumu- 

 lating those chemical treasures that in the fulness of years 

 will perhaps burst into an orchid blossom. 



The terrestrial orchids all grow as other earth-growing 

 plants do, with roots closely resembling those of the lily 

 family, sometimes fibrous, sometimes fleshy, sometimes 

 bulbous. In most cases when one of these high-bred epiph- 

 etal orchids living on dew and sunshine is brought suddenly 

 to earth, planted" in soil and forced to live the life of its more 

 mundane neighbours, it dies, but there are instances of a few 

 aerial species that can adapt themselves to circumstances, and 



